Propeller construction

ABSTRACT

An improved structure for a through-the-hub exhaust-type propeller made of a glass filled nylon. An aluminum liner is molded within the center bore of the hub structure to provide uniformity, add strength and provide predictable slip resistance to a layer of impact absorbing material disposed between the liner and an inner sleeve attached to the propeller drive shaft. A deflecting ring may be attached to the outer casing of the hub by flaring the trailing edge of the outer casing with a heated cone; or the outer casing itself may be so flared to create a deflecting ring.

United States Patent 11 1 Frazzell et al.

[ PROPELLER CONSTRUCTION [75] Inventors: Michael E. Frazzell, Neenah;

Richard H. Snyder, Oshkosh, both of Wis.

[73] Assignee: Brunswick C0rp., Skokie, Ill.

[22] Filed: Aug. 2, 1973 [21] Appl. No.: 385,170

[52] US. Cl 416/93, 416/134, 416/230, 416/241 [51] Int. Cl. B63h H28 [58] Field of Search..... 416/93 M, 230, 241 A, 134, 416/169 [56] References Cited UNITED STATES PATENTS 3,033,293 5/1962 Bihlmire 416/236 X 3,279,415 10/1966 Kiekhaefer 416/93 M 3,318,388 5/1967 Bihlmire 416/240 X 1451 Feb. 11,1975

3,487,804 l/l970 Kiekhaefer 416/93 M UX 3,563,670 2/1971 Knuth 416/134 UX 3,758,231 9/1973 Barnstead 416/241 A UX Primary Examiner-Everette A. Powell, Jr. Attorney, Agent, or Firm-William G. Lawler, Jr.

[57] ABSTRACT An improved structure for a through-the-hub exhausttype propeller made of a glass filled nylon. An aluminum liner is molded within the center bore of the hub structure to provide uniformity, add strength and provide predictable slip resistance to a layer of impact absorbing material disposed between the liner and an inner sleeve attached to the propeller drive shaft. A deflecting ring may be attached to the outer casing of the hub by flaring the trailing edge of the outer casing with a heated cone; or the outer casing itself may be so flared to create a deflecting ring.

PROPELLER CONSTRUCTION BACKGROUND OF THE INVENTION Through-the-hub exhaust propellers such as that illustrated in U.S. Pat. No. 3,563,670 made of aluminum, steel or bronze have gained broad acceptance for use on outboard motors and marine stern drive units. Numerous attempts have been made to manufacture propellers out of synthetic materials and considerable success has been achieved with polycarbonate. However, polycarbonate is not suitable for through-the-hub exhaust-type props as it is attacked by fuel residue and products of combustion.

U.S. Pat. Nos. 3,033,293 and 3,318,388 teach fabrication of propellers similar to that of the invention, except that they are not of the through-thehub exhaust type and employ structures and materials differing from those which the Applicant has found to materially improve the performance of propellers of this type.

Accordingly, one problem which confronted the Applicant was finding a material, which when molded to the desired size and shape would exhibit the qualities of durability desired, and at the same time be resistant to engine exhaust and residual fuel elements.

Another problem in the development of such a propeller was the design of an inner hub structure to provide a resilient connection between the propeller and the propeller drive shaft to protect the motor from sudden stoppage of the propeller.

It is, therefore, an objective of the invention to provide a propeller of synthetic material which exhibits certain properties of strength and durability which exceed such properties of aluminum propellers of equivalent shape and size.

It is another objective of the invention to provide a more durable and effective resilient coupling between the synthetic propeller and its drive shaft.

It is a further objective of the invention to teach a novel construction of, and method of attaching, a deflector ring to the propeller hub.

SUMMARY OF THE PRESENT INVENTION- Basically the invention comprises a through-the-hub exhaust-type propeller molded of a glass filled nylon blended with an ionomer resin. A hub is suspended within an outer annular casing by a series of webs. A metal sleeve molded within the center hub structure provides a bearing surface for a resilient member compressed between said liner and an inner sleeve adapted to receive the propeller drive shaft. The resilient member may be bonded to the inner sleeve or compressed upon assembly. A molded deflector ring may be lodged in an annular groove in the trailing edge of the outer annular casing of the hub and retained in place by hot swaging the trailing edge of said casing against the inner wall of the deflector ring; or, the trailing edge of the outer casing may be similarly flared to create an integral deflector ring.

Primary advantages of the propeller of the invention are its resistance to plastic deformation, its light weight and longer life. The light weight reduces shifting loads on the engine drive train, due to less inertia of the prop, and the effect of any imbalance within the propeller such as that produced by nicks or chipping.

Another advantage of the invention is that it provides a mounting assembly which effectively supports the plastic propeller without endangering the engine to which it is attached by sudden stoppage.

A further advantage of the invention lies in the simple and economical method of manufacture of a propeller and its deflector ring.

Other objectives, advantages, and various further features of novelty and invention will be pointed out or will occur to those skilled in the art from a reading of the following specification in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal cross-section of a propeller hub of the invention.

FIG. 2 is a lateral cross-sectional view of a hub of the invention taken generally along line 2-2 of FIG. 1.

FIG. 3 is a longitudinal cross-sectional view of the trailing edge of the hub of FIG. 1 prior to the rolling out of the trailing edge of the hub to secure the deflector rmg.

DETAILED DESCRIPTION OF THE DRAWING Referring to FIG. 1, the propeller hub l and blades 2 are injection molded by methods known to the art as a single unit. The preferred material is a polyamide such as that described in published Dutch patent application 67-05,239 filed by E. I. du Pont dc Nemours & Co., the subject matter of which is incorporated herein by reference, and sold under the trade name of Zytel This material consists of an intimate mixture of (a) 99 percent wt. of a polyamide, and (b) 1-50 percent by weight of an ionic copolymer derived from a C a-alkene, and 02-25 molecular percent of an a,/3-alkenically unsaturated carboxylic acid, at least 10 percent of the acidic groups in the copolymer being neutralized by metal ions. The polyamide is preferably polyhexamethyleneadipamide. The copolymer is preferably based on ethylene, and methacrylic or maleic acid. The metal ions are preferably Zinc ions. The compound may also contain an antioxidant.

Glass fiber reinforcement must be added to achieve the desired strength and durability. Applicant has found that 33 percent by weight is the optimum quantity of such fill to produce maximum durability; however, a range of between 30 percent and 50 percent by weight will produce an acceptable product, with slightly different characteristics of flexiblity and hardness occurring within the range.

This material is well suited to injection molding, particularly when lubricated with a saturated fatty acid such as aluminum stearate.

The hub 2 includes an outer annular casing 3 and an inner hub 4 supported by the three webs 5. During the molding process, a sleeve 10, preferably but not necessarily of aluminum, is molded within the hub 4 and provides a uniform bore 11 therein. A smaller bore 12 is provided in the after end portion of the hub 4.

An inner sleeve 14 having splines 15 internally thereof extends within the bore 11 and fits snugly within the bore 12.

An annular resilient element 16 extends around the inner sleeve 14 and is compressed between the inner surface of the bore 11 and the outer surface of the splined sleeve 14. The resilient member 16 may be a natural rubber bonded to an aluminum sleeve 14, the combination of which is press fitted within the bore 11.

The outer surface of the cylindrical liner may be scalloped to provide indentations into which the molten material flows during the molding process; therebyeliminating any possibility of slippage of the liner 10 within the hub 4.

The sleeve 10 performs at least three recognized functions:

1. It adds hoop strength to the hub 4 and in particular prevents cold flow of the nylon material of the hub which could occur if the resilient element 16 were allowed to bear directly against the bare hub.

2. It provides a bore 11 of uniform dimension. Due to the shape of a propeller and the characteristics of the nylon material, a hole in the center may not cure to uniform dimension.

3. It provides a predictable coefficient of friction for the outer surface of the resilient element 16, an effect which may be difficult to achieve with random exposure of glass fibers in the surface of the nylon.

A propeller made of the aforementioned material is not subject to plastic or permanent deformation. Contact with under water objects may cause a portion 9 of the propeller blade to chip away; however, it is very much more resistant to chipping than its aluminum counterpart is to a bending or deformation of its blade edges. Due to the reduced weight of the material, any chips or nicks that do occur have considerably less effect upon the balance of the prop than deformation or loss of material of its metal counterpart.

A propeller made of the aforementioned material is approximately one-half the weight of its aluminum counterpart, and because of its resistance to corrosion and errosion will have a considerably longer life.

Referring to FIG. 2 the scallops 17 appear on the outer cylindrical surface of the liner 10. The splined sleeve 14 and the natural rubber impact absorbing element 16 are in place within the bore 11. Ideally the hub 4 is supported by three or more webs 5 which are integrally molded with the remainder of the hub and blades of the propeller; the number being determined by the number of blades. It has been found that less deformation in molding results when the number of webs equals a multiple of the number of blades, except that at least three webs are required to prevent egging of the hub of a two bladed propeller.

Referring to FIG. 3, a process of securing a deflector ring 20 to the outer annular casing 3 of the propeller hub is illustrated. Upon molding of the propeller, the trailing edge 21 of the annular casing 3 is left straight or cylindrical, and has an annular step 22 molded into its trailing edge. A deflector ring, preferably made of type 6/6 nylon, is separately molded with an interior diameter such that the ring 20 slides snugly into the annular step 22 of the casing 3. An object 23 having a tapered surface, such as that shown in phantom in FIG. 3, heated to a temperature sufficient to render the plastic material of the propeller deformable, is inserted in the open end 24 of the propeller hub until its surface 26 heats the trailing edge 21 of the casing 3 and flares it outwardly against the inner surface of the deflector ring 20 as illustrated in FIG. 1. Alternately the trailing edge 21 may itself be flared outwardly to form a deflector ring, the purpose of which is to give the water flowing thereover an outward component of motion which in turn inhibits exhaust from being drawn forward to the low pressure side of the propeller blades. Those skilled in the art will know the temperature to which the trailing edge 21 should be subjected to produce such deformation.

While the principles of the invention have been described in connection with the above specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation to the scope of the invention.

I claim:

l. A through-the-hub exhaust type marine propeller comprising a hub and blades integrally molded of nylon reinforced by greater than thirty percent by weight of fiberglass, said hub including an outer cylindrical housing, an inner hub portion and a plurality of webs supporting said inner portion within said housing.

2. The device of claim 1 wherein the number of said webs is equal to a multiple of the number of blades on the propeller but in no case less than three.

3. The device of claim 1 wherein said inner hub portion further includes a second and smaller centering bore, a cylindrical tube adapted to fit within said second bore, and a layer of resilient shock absorbing material compressed between said liner and said tube.

4. A through-the-hub exhaust-type propeller for marine power plants comprising an inner hub, an outer cylindrical member surrounding said hub,

a plurality of webs connecting said inner hub and outer member,

said propeller being integrally molded of a composition comprising 55-99 percent by weight polyamide, and 1-50 percent by weight ionic copolymer, and having mixed therewith 30 percent by weight of glass fibers, and

the number of said webs being equal to a multiple of the number of blades of the propeller.

5. The propeller of claim 1 wherein said composition further includes 0.2-25 molecular percent unsaturated carboxylic acid, and has between thirty and fifty percent by weight of fiberglass dispersed therein.

6. The propeller of claim 1 having about thirty-three percent by weight of fiberglass dispersed therein.

7. A through-the-hub exhaust type marine propeller molded of synthetic material and comprising a central hub portion having a first bore therein,

a cylindrical liner molded within said first bore,

a tubular section concentric and within said liner, and a layer of resilient material disposed generally between said liner and said tubular section.

8. The propeller of claim 7 wherein said tubular section comprises means interior thereof to engage a propeller drive shaft.

9. The propeller of claim 7 further comprising an outer cylindrical hub means to confine the flow of exhaust gases around said central hub, said outer cylindrical hub having a flared trailing edge so as to deter exhaust gases from being drawn forward to the low pressure side of the propeller blades. I

10. The propeller of claim 9 wherein an end portion of said outer cylindrical hub means is hot swaged outwardly forming a deflector ring thereon.

11. A method of providing a deflector ring in a molded plastic propeller comprising the steps of,

providing a through-the-hub exhaust-type propeller having a central hub surrounded by an outer cylindrical element,

providing a body having a tapered surface of revolution,

heating said body to a temperature sufficient to plastically deform said outer cylindrical element, and

inserting said heated body symetrically within the after end of said cylindrical element, whereby the after end of said element is flared outwardly forming a deflector ring in the propeller hub. 

1. A through-the-hub exhaust type marine propeller comprising a hub and blades integrally molded of nylon reinforced by greater than thirty percent by weight of fiberglass, said hub including an outer cylindrical housing, an inner hub portion and a plurality of webs supporting said inner portion within said housing.
 2. The device of claim 1 wherein the number of said webs is eqUal to a multiple of the number of blades on the propeller but in no case less than three.
 3. The device of claim 1 wherein said inner hub portion further includes a second and smaller centering bore, a cylindrical tube adapted to fit within said second bore, and a layer of resilient shock absorbing material compressed between said liner and said tube.
 4. A through-the-hub exhaust-type propeller for marine power plants comprising an inner hub, an outer cylindrical member surrounding said hub, a plurality of webs connecting said inner hub and outer member, said propeller being integrally molded of a composition comprising 55-99 percent by weight polyamide, and 1-50 percent by weight ionic copolymer, and having mixed therewith 30 percent by weight of glass fibers, and the number of said webs being equal to a multiple of the number of blades of the propeller.
 5. The propeller of claim 1 wherein said composition further includes 0.2-25 molecular percent unsaturated carboxylic acid, and has between thirty and fifty percent by weight of fiberglass dispersed therein.
 6. The propeller of claim 1 having about thirty-three percent by weight of fiberglass dispersed therein.
 7. A through-the-hub exhaust type marine propeller molded of synthetic material and comprising a central hub portion having a first bore therein, a cylindrical liner molded within said first bore, a tubular section concentric and within said liner, and a layer of resilient material disposed generally between said liner and said tubular section.
 8. The propeller of claim 7 wherein said tubular section comprises means interior thereof to engage a propeller drive shaft.
 9. The propeller of claim 7 further comprising an outer cylindrical hub means to confine the flow of exhaust gases around said central hub, said outer cylindrical hub having a flared trailing edge so as to deter exhaust gases from being drawn forward to the low pressure side of the propeller blades.
 10. The propeller of claim 9 wherein an end portion of said outer cylindrical hub means is hot swaged outwardly forming a deflector ring thereon.
 11. A method of providing a deflector ring in a molded plastic propeller comprising the steps of, providing a through-the-hub exhaust-type propeller having a central hub surrounded by an outer cylindrical element, providing a body having a tapered surface of revolution, heating said body to a temperature sufficient to plastically deform said outer cylindrical element, and inserting said heated body symetrically within the after end of said cylindrical element, whereby the after end of said element is flared outwardly forming a deflector ring in the propeller hub. 